Liquid crystal display and driving method thereof

ABSTRACT

A liquid crystal display includes m valid gate lines G 1  to Gm arranged in a first direction with first constant intervals between gate lines, n valid data lines arranged in a second direction perpendicular to the valid gate lines with second constant intervals between data lines, and at least one dummy data line at a periphery of and in parallel with the n valid data lines. A method of driving a liquid crystal display is carried out by a general procedure of shorting the dummy data lines with a specific data line or by applying the same driving signals of a specific data line to the dummy data line.

This application is a divisional of U.S. patent application Ser. No.10/948,291, filed Sep. 24, 2004, now U.S. Pat. No. 7,119,783 which is adivisional of U.S. patent application Ser. No. 10/017,583, filed Dec.18, 2001, now U.S. Pat. No. 6,812,908, issued Nov. 2, 2004, which claimthe benefit of Korean Patent Application No. P2000-83095, filed on Dec.27, 2000, which are hereby incorporated by reference for all purposes asif fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a displaying apparatus, and moreparticularly to a liquid crystal display and driving method thereof.

2. Background of the Related Art

Generally, a liquid crystal display (LCD) includes a thin filmtransistor (TFT) liquid crystal display (TFT-LCD) panel, a backlightunit, and a driver. The TFT-LCD panel may have degradations as follows:first, degradation of characteristic values from standard design due toprocess deviations; second, degradation due to dust, poor cleaning at afilm surface, and the like; and, third, degradation of characteristicvariations due to static electricity and breakdown of thin filmtransistors or liquid crystal cells.

One of the degradations occurring in a TFT-LCD panel is the irregularityof combining a first substrate with an opposed second substrate, whichresults in reducing the sharpness of a displayed video or in leakinglight when failing to meet the design margin.

Reference will now be made in detail to an LCD according to a relatedart, examples of which are illustrated in the accompanying drawings.

FIG. 1 shows a layout of an LCD according to a related art.

Referring to FIG. 1, a liquid crystal display generally comprises anumber of ‘m’ gate lines G1 to Gm arranged in a first direction with aconstant interval between the gate lines; a number of ‘n’ data lines D1to Dn arranged in a second direction perpendicular to the respectivegate lines G1 to Gm with a constant interval between the data lines; aplurality of pixel electrodes (not shown in the drawing) formed as amatrix in pixel areas defined by the crossing gate and data linesrespectively; and a plurality of thin film transistors for applying datasignals supplied through the respective data lines to the respectivepixel electrodes by being switched according to signals of the gatelines.

Further, a pair of driver integrated circuits (ICs) 14 and 15 areinstalled at the sides of the gate and data lines, respectively, so asto supply gate and data driving signals thereto. Namely, a pair of pads(not shown in the drawing) are formed at the ends of the gate and datalines to which the driver ICs are connected.

FIG. 2 shows cross-sectional views of the LCD taken along a line I-I′ inFIG. 1.

Referring to FIG. 2, a gate insulating layer 22 is formed on a firstsubstrate 21. An nth data line 23 is patterned on the gate insulatinglayer 22. A passivation layer 24 made of an insulator is formed over anentire surface of the substrate including the nth data line 23. Atransparent conductive layer of indium tin oxide (ITO) 25 for applying avoltage to the liquid crystal display is patterned on the passivationlayer 24.

A black matrix 27 having predetermined spaces therein, is formed on anupper insulating substrate 26. A color filter layer 28 fills the spacesin the black matrix 27.

Unfortunately, the LCD according to the related art has some problems asfollows.

The degree of alignment for the TFT and color filter substrates dependson the alignment tolerance (or margin) for combining (or assembling) theupper and lower substrates. Such combining margin is determined by thedesign of the respective substrates, for which precision of aboutseveral micrometers is required. Light leakage occurs at both lateralsides of the panel when the alignment between two substrates is deviatedfrom the combining margin, thereby failing to provide desirable drivingcharacteristics.

Namely, as shown in FIG. 2, there is no structure to block the lightleakage at the right side of the nth data line 23. Therefore, lightleakage occurs due to the transmitting light reaching the color filterlayer.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a liquid crystaldisplay and driving method thereof that substantially obviates one ormore of the problems due to limitations and disadvantages of the relatedart.

An advantage of the present invention is to provide the provision of aliquid crystal display and driving method thereof, in which additionaldummy gate and data lines are formed to prevent light leakage at bothlateral sides of the panel due to the combining irregularity of thepanels.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages, and in accordance with thepurpose of the present invention as embodied and broadly described, aliquid crystal display according to the present invention includes mvalid gate lines G1 to Gm arranged in a first direction with firstconstant intervals between the valid gate lines; n valid data linesarranged in a second direction perpendicular to the valid gate lineswith second constant intervals between the valid data lines; and atleast one dummy data line at a periphery of and in parallel with the nvalid data lines.

In another aspect of the present invention, a liquid crystal displayaccording to the present invention includes m valid gate lines G1 to Gmarranged in a first direction with first constant intervals between thevalid gate lines; n valid data lines arranged in a second directionperpendicular to the valid gate lines with second constant intervalsbetween the valid data lines; a dummy gate line in parallel with thevalid gate lines at a periphery of the m valid gate lines; and at leasta first and a second dummy data line at left and right sides of the nvalid data lines.

In a further aspect of the present invention, a liquid crystal displayin a TFT-LCD panel includes a first substrate on which a black matrixlayer and a color filter layer are stacked sequentially on a firstinsulating substrate; a second substrate on which a gate electrode, agate insulating layer, an active semiconductor layer, source and drainelectrodes, and a passivation layer are stacked on a second insulatingsubstrate, wherein the second substrate opposes the first substrate; anda liquid crystal layer between the first and second substrates, whereinthe passivation layer is formed of an organic insulating material.

In another further aspect of the present invention, a method of drivinga liquid crystal display including a valid data line area in which aplurality of data lines D1 to Dn are formed; areas of a first dummy dataline and a second dummy data line formed at left and right sides of thevalid data line area; a valid gate line area in which a plurality ofgate lines G1 to Gm are formed; and a first dummy gate line formed atone side of the valid gate line area, includes applying a first samedriving signal to the first dummy data line and a second data line D2 ina plurality of the data lines and a second same driving signal to thesecond dummy data line and (n−1)th data line Dn-1, and applying a pulsewaveform synchronized to a waveform applied to the mth gate line Gm tothe dummy data lines.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 shows a layout of LCD according to a related art;

FIG. 2 shows a cross-sectional view of the LCD taken along a line I-I′in FIG. 1;

FIG. 3 shows a layout of a liquid crystal display according to a firstembodiment of the present invention;

FIG. 4 shows a layout of a liquid crystal display according to a secondembodiment of the present invention;

FIG. 5 shows a timing graph of gate driving signals in a liquid crystaldisplay according to the present invention;

FIG. 6A shows a layout of a magnified area II-II′ in FIG. 3; and

FIG. 6B shows a cross-sectional view the LCD taken along a line III-III′in FIG. 6A.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. Where possible, the same reference numerals will be used toillustrate like elements throughout the specification.

In the present invention, it is intended that forming additional dummygate and data lines prevents light leakage at both lateral sides of thepanel due to the combining irregularity of the panels.

FIG. 3 shows a layout of a liquid crystal display according to a firstembodiment of the present invention.

Referring to FIG. 3, a panel according to the present invention includesa valid data line area 31 in which a plurality of even-numbered andodd-numbered data lines D1′ to Dn are separated from each other by aconstant interval between data lines; a first dummy data line area 32 aand a second dummy data line area 32 b formed outside the valid dataline area 31; a valid gate line area 33 where a plurality of gate linesG1 to Gm are formed in a direction crossing with the data lines withconstant intervals between adjacent gate lines; and a first dummy gateline area 34 outside the valid gate line area 33.

In this case, the first dummy data line formed in the first dummy dataline area 32 a is connected with the second data line D2 in the validdata line area 31 through a first conductive line 35. The second dummydata line formed in the second dummy data line area 32 b is connectedwith the (n−1)th data line Dn-1 in the valid data line area 31 through asecond conductive line 36.

Therefore, the first dummy data line formed in the first dummy data linearea 32 a is supplied with the same data signal as applied to the seconddata line D2, while the second dummy data line in the second dummy dataline area 32 b is supplied with the same data signal as applied to the(n−1)th data line Dn-1.

The LCD according to the present invention is driven by the datainversion method. Thus, the first data line D1 is positive (+) and thesecond data line D2 is negative (−), thereby resulting in thealternation of (+) and (−) in a plurality of the data lines formed inthe valid data line area 31.

Accordingly, the first dummy data line in the first dummy data line area32 a is driven in a manner opposite to that of the first data line D1,while the second dummy data line in the second dummy data line area 32 bis driven in a manner opposite to that of the nth data line Dn.

The LCD having the above structure is driven in a manner as follows.

First, as shown in FIG. 3, the first dummy data line is connected to thesecond data line D2 through the first conductive line 35, and the seconddummy data line is connected to the (n−1)th data line Dn-1 through thesecond conductive line 36. In this case, data signals are outputted fromthe driver by a general method.

Therefore, the effective width of the display is broadened by drivingall the pixels of the display because the data lines including the firstand second dummy data lines are driven in accordance with thealternating of (+) and (−).

FIG. 4 shows a layout of a liquid crystal display according to a secondembodiment of the present invention.

Referring to FIG. 4, the structure of a panel in an LCD according to thesecond embodiment is the same as that of the panel of the firstembodiment, except for the formation of the first and second conductivelines. In such a structure, a data driver circuit supplies video signalsso that one signal is applied to the first dummy data line and thesecond data line D2, and another signal is applied to the second dummydata line and the (n−1)th data line. The first dummy data line and thesecond dummy data line are supplied with video signals having differentpolarities respectively. The data driver applies the same video signalsto the second data line D2 and the first dummy data line and appliesanother identical video signal to the (n−1)th data line Dn-1 and thesecond dummy data line. A voltage difference between high and lowlevels, ΔV_(ghl)(=V_(gh)−V_(gl)), applied to the first dummy gate lineis equal to or higher than about 1 V.

In this case, a gate driving signal for driving the first and seconddummy data lines and the valid data line is explained in the followingdescription.

FIG. 5 shows a timing graph of gate driving signals in a liquid crystaldisplay according to the present invention.

Referring to FIG. 5, the time at which a driving signal is applied tothe first dummy gate line 34 is synchronized with the time at which adriving signal is applied to the mth gate line Gm placed at the end ofthe panel.

Namely in the panel, when the driving signal is finally applied to themth gate line Gm through a plurality of valid gate lines G1 to Gm fromthe first dummy gate line 34, the same signal is applied to the firstdummy gate line 34.

FIG. 6A shows a layout of a magnified area II-II′ in FIG. 3 and FIG. 4.

Referring to FIG. 6A, a pixel electrode 66 and a thin film transistor 13are formed in a pixel area defined by an nth data line Dn 63, a seconddummy data line 32 b, and a pair of valid gate lines 33 crossing withthe nth data line Dn and the second dummy data line 32 b.

FIG. 6B shows a cross-sectional view the LCD taken along a line III-III′in FIG. 6A.

Referring to FIG. 6B, a gate insulating layer 62 is formed on aninsulating substrate 61 as a lower substrate. The nth data line 63 andthe second dummy data line 32 b are formed on the gate insulating layer62 a predetermined interval apart.

A passivation layer 65 is formed on the substrate including the datalines with an organic insulating material such as BCB (benzocyclobutene)or acrylate or an inorganic insulating material such as silicon nitride(SiN_(x)).

A transparent conductive layer 66 of ITO for applying voltage to theliquid crystal display is formed on the passivation layer 65.

A black matrix 68 having a space therein is patterned on the otherinsulating substrate 67 as an upper substrate. A color filter layer 69is formed on the substrate 67 including the black matrix 68.

The second dummy data line 32 b formed in the above structure preventslight transmission within a visible angle at the edge of the panel anddrives the pixel at the lateral sides of the second dummy data line,which also occurs in an area where the first dummy data line is formed.

Accordingly, the LCD according to the present invention prevents lightleakage due to the combining irregularity by adding the dummy data linesand dummy gate lines, as well as substantially widening the display bydriving the pixels next to the dummy data line when applying signals tothe dummy data line.

It will be apparent to those skilled in the art that variousmodifications and variation can be made in the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A liquid crystal display in a TFT-LCD panel, comprising: a firstsubstrate in which a black matrix layer and a color filter layer arestacked sequentially on a first insulating substrate; a second substrateon which a gate electrode, a gate insulating layer, at least one validdata line and at least one dummy data line adjacent the at least onevalid data line, an active semiconductor layer, source and drainelectrodes, and a passivation layer are stacked on a second insulatingsubstrate, wherein the second substrate opposes the first substrate; anda liquid crystal layer between the first and second substrates, whereinthe at least one dummy data line prevents light transmission within avisible angle at an edge of the TFT-LCD panel.
 2. The liquid crystaldisplay of claim 1, wherein the passivation layer is formed of anorganic insulating material.
 3. The liquid crystal display of claim 1,wherein the passivation layer is formed of an inorganic insulatingmaterial.
 4. The liquid crystal display of claim 3, wherein theinorganic insulating material is silicon nitride (SiN_(x)).
 5. A liquidcrystal display, comprising: a gate insulating layer formed on a firstinsulating substrate; a plurality of data lines Dl through Dn, wherein adummy data line and at least one_ of the first data line and the nthdata line are formed on the gate insulating layer a predeterminedinterval apart; a passivation layer formed on the first insulatingsubstrate including the data lines; a transparent conductive layer forapplying voltage to the liquid crystal display formed on the passivationlayer; a black matrix having a space therein patterned on a secondinsulating substrate; and a color filter formed on the second insulatingsubstrate including the black matrix, wherein the dummy data lineprevents light transmission within a visible angle at an edge of theliquid crystal display.
 6. The liquid crystal display of claim 5,wherein the passivation layer is one of BCB (benzocyclobutene) andacrylate.
 7. The liquid crystal display of claim 2, wherein the organicinsulating material is one of BCB (benzocyclobutene) and acrylate. 8.The liquid crystal display of claim 5, wherein the passivation layer issilicon nitride (SiN_(x)).